The 40-year old is set for a Celtic Park return on the weekend when he and his Dundee teammates take on the Bhoys in the Scottish Premier League and he only had positive words to say about ex-Newcastle United gloveman Forster who was at the forefront of a clean sheet against Benfica in the Champions League on Wednesday.
"I've been impressed with Fraser whenever I've seen Celtic," Douglas said.
"I was at the Benfica game and he did well again. It was another very important clean sheet.
"He's had four in five European games now this season and that's outstanding by anyone's standards.
"It took him a little while to settle, but he's proved to be an excellent goalkeeper over the last two years.
"It says it all about his performances that Ray Clemence came up to watch him against Benfica for England. Hopefully, he'll get a call-up.
"I know exactly the pressure that is on you as a Celtic goalkeeper and the character you have to show, especially when things aren't going well.
"But he looks as if he's got all the right qualities. Our front boys will have their work cut out trying to beat him on Saturday.
"It was his Champions League debut and I knew exactly how he would have been feeling.
"It was incredible for me. You know it's a massive moment in your career. Fraser's come through it well and will be all the better for it."